Telemetering system and apparatus



Nov. 29, 1938. E, W T 2,138,668

TELEMETERING SYSTEM AND APPARATUS Filed Sept. 10, 1936 Insular/017 Invehtor Clyde E. Stewart,

by Z I-hs Att ovne y.

Patented Nov. 29, 1938 UNITED, STATES 2,138,668 a a a TELEMETERING SYSTEM AND APPARATUS Clyde E. Stewart, Upper Darby, Pa assignorto a General Electric Company, a corporation of ,New York Application September 10,1936, SerialNo.100,151 8 Claims (01. 177- 351) My invention relates to telemetering apparatus and its use in a telemetering system and its object is to provide simple but reliable" apparatus of this class which is applicable to avwide variety of In carrying my invention into effect in its preferred form, I employ a transmitter for opening and closing the telemetering circuit intermittently and varythe ratio of the time'the circuit is open to the time it is closed in response to variations in the condition or measurement to be transmitted. At the receiving station, a relay is provided foralternately energizing a. differentialmeasuring system such as opposed thermocouple heater circuits in accordance with circuit-open and circuit-closed periods of the transmitter. These thermocouples then energize an instrument calibrated in terms of the condition or measurement thus transmitted.

The features of my invention which are believed to be novel and patentable will be pointed out in the claims appended hereto. For a better understanding of my invention, reference is made in the following description to the accompanying drawing wherein Fig. 1 illustrates. a complete telemetering system according to the present in vention; Figs. 2 and 3 show side and'pla'n views of a transmitter for transmitting impulses indicative of water level; and Fig. 4 shows a system ar- 30 ranged for transmitting a plurality .of diflerent indications to a plurality of different points.

In Figure l, a transmitter-commuta'ting disk Ill is shown connected'to the telemetering circuit H which runs to a relay l 2 at a distant receiving sta- 35 tion. 13 indicates a source of supply for the relay telemetering circuit and also for the 'circuit of two heaters M and I5 which are alternately en-,

relay I2, the source of supply I3, heaters and; I5, the thermocouples, and the millivoltmeter 25 will be located at the receiving station. a

The commutator disk ill at the transmitting station is rotated at a uniform speed. It is provided with a'conducting surface 26over one half of its periphery and with an insulating surface 21 over the other half of its periphery. The conducting portion 26 is electrically connected to the shaft 28 omwhich bears a brush 29 connected to one side of the telemetering circuit ll. Bearing on the periphery of the disk is a" brush 30 which in most cases will be stationary and a brush .3lwhich may be adjustedfrom brush 30 about the periphery, approximately 180 degrees. .Brushes 30 and 3| are connected together by wire 32and to the other 'side'of the telemetering circuit II. The direction of rotation of thedisk I0 is immaterial. Its rate of rotatin may be one revolution per secondmore or less aslong as it is constant,

It will now be evident that, when brush 3| is moved around to the same point occupied by stationary-brush 30, the telemetering circuit II will be closed for one-half revolution of the disk when the conductingportion 26is passing under the brushes and will be open for the other half of a revolution While the insulating. part 21 is passing under the brushes. Thus, under such conditions, relay l2 will be energized for a half second and deenergized for the nextphalf second and 'so on, or, in 0th8T W0rdS,-it will be energized exactly one half ;the time. Consequently, heater will be energized intermittently when the relay is energized forhalf the time and heater I5 will be intermittently energized when the relay-is deenergized for the remainder of 'the time from the same source l3 and, consequently, the average heating effects on thermocouples 2| and 22- will be equal, thevoltages produced thereby will be equal and opposite, and the differential millivoltmeter'25 will read zero. Calibrating resistances 33 and 34' may be. provided in the heater circuits, if necessary, to equalize any unbalance in the calibration under thesecircumstances.

If now we move adjustable contact 3| away fromstationary contact 30 aboutthe periphery of the disk, the time during which relay I2 is energized will increase and the time during which it is deenergized will decrease during each revolution of the disk. This is because the brushes are in parallel. The effect is the same as if we had only one brush of varying width such-as to span the are between the two brushes 30 and 3|;

If we move brush 3| around degrees tothe position indicated in the drawing, the relay telemetering circuit will be closed three-fourths of the time since it takes three-fourths 'of a revolu tion of the disk to move the conducting segment 26 past both brushes 30 and 3|. For instance, if the disk rotates .clockwise from the position shown, brush 30 will remain in contact with conducting segment 26 for one-half revolution but,

' will be indicated by instrument 25.

when the disk has made one-fourth revolution, brush 3| willengage the conducting segment 26 and then remain in contact for one-half revolution so that contact is made at one point or the other for three-fourths of a revolution.

If we move brush 3| around to the 180 degree point from brush 30, brush 30 will break contact with segment 26 at the same instant brush 3| makescontact therewith so that the telemetering relay circuit II will be closed continuously under such conditions. When this happens, heater l4 at the receiving station will be energized continuously and heater l5 not at all and the instrument is so calibrated with the thermocouples as to produce a full scale deflection under such conditions. It will now be seen that, with proper calibration, instrument 25 produces a deflection from zero to full scale as brush 3| moves from brush 3!) about the disk to the 180 degree point, and produces a straight line proportionate deflection for any intermediate position of brush 3|. It remains only to move brush 3| from brush in proportion to some change or measurement to be transmitted, and such change or measurement It will, of course, be evident that brush 3| may be moved by hand but it will generally be preferable to move it automatically'in response to the condition or measurement to be transmitted.

Figs. 2 and 3 show one way in which this may be done automatically and also other details of construction of the transmitter. 'As shown in Fig. 3, the shaft 28 of the transmitter is driven through suitable reduction gearing 33 by a small constant-speed motor 34. The disk ll! of Figrl is secured to shaft 28 and is made of a central insulating layer 21:: and outer segmental conducting layers 26a and 26b suitably clamped together. The two conducting segments are'electrically con nected together by the shaft 28 and through a slip ring to the brush 29 to 'one side of the telemetering circuit The stationary brush 30 overlaps conducting segment 26a and a portion of the circular insulating disk 21a. The movable brush 3| overlaps conducting segment'26b and a portion of the insulating disk 21a. By this arrangement, brush 3| may be moved adjacent-and inline with brush 30 without'interference and also the brushes are maintained in their radial positions, moving smoothly 'on and off the conducting segments as the disk rotates.

The movable brush-3| is supportedon an arm 36 that is arranged to be adjusted about shaft 28' in response to the measurement to be transmitted. In this case, the device is arranged to transmit an indication of water level, and arm 36' is secured to a drum 3'! about which is wound a cable 38 connected at one end to the float 39 and at the other end to a weight 40. The drum is free to turn on an extension of shaft 28. Its arm 36 is suitably insulated from the shaft and is con nected through the flexible cable 32 in parallel with stationary brush 30 to the other side of the telemetering circuit I I.. It will be evident now that the brush 3| will be rotated away from brush 30. as the water level at 4| rises. The instrument 25, Fig. 1, may then be calibrated to indicate water level or such other variable condition as may be caused to rotate movable brush arm 36.

The transmitting system is capable of considerable flexibility.- For example, it will be observed in Fig. 1 that it is immaterial which way the movable brush 3| is moved about the. commutator from the stationary brush 30 and, for some telemetering purposes, it. may have a range of moverection in accordance with one, variable and we give brush 30 a range of movement from this same point ninety degrees in a counterclockwise direction in accordance with another variable, the transmission impulses will vary in the same way as before but in accordance with the sum of the two variables. If bothbrushes are movable in the samedirection from the same zero-transmitting point in accordance with two variables, the transmission impulses will vary in the same way as before but in accordance with the difference of the two variables. The range of movement ofthe brushes in this case may be 180 degrees. No change is required in the receiving apparatus when the transmitter is used to transmit the sum or difi'erence of two variables;

; The transmitter may be arranged to transmit two or more variables without correspondingly duplicating all of its parts as will be explained in connectionwith Fig. 4. 1

The receiver may produce an integrating measurement, a number of receiving relays may be connected in series or in parallel and be located at different receiving points, separate sources of supply may be used for the telemetering relay circuit and for the receiving apparatus, as will be explained in connection with' Fig 4, and it will be obvious that the telemetering channel may be of the carrier-current type if desired.

In Fig. 4, there is included a systemsuch as has already been described in connection with Fig. l and the similar parts are designated by like reference characters. 7

The rotary transmitting disk I0 is provided with an extra set of stationary and movable brushes 43 and 44, respectively, for transmitting be provided to transmit a corresponding number of different measurements simultaneously. It will be evident that, in Fig. 4,the brushes 43 and 44 may be used to transmit one measurement while the brush set 30 and 3| is transmitting some independent measurement. The two transw mitting channels use the same source of supply l3 and the common transmitting wire leading to brush 29.

The receiving relay 45 is similar to the relayl2 already described except that it has a double set of contacts. However, one of the receivers controlled by relay 45 is arranged to integrate the measurement received. In this case, the receiver comprises a pair of similar motorssuch as similar self-starting synchronous motors 46 and "having their rotors connected to the same shaft 48, driving a common counter 49. The motors, when energized, operate in opposite directions. They are supplied from a common alternating-current source 5|! through the upper set of contacts of relay 45; and due to the operation of the'relay 45, the motors are energized alternately as the relay is energized and deenergized. As shown, the relay is energized and motor 41 is energized through the upper relay contact. Motor 4'! drives register 49 in the forward direction and it will be noted from the position of movable brush 44, which is about 90 degrees removed from its companion stationary brush 43, that the transmitted measurement is about half way between zero and maximum value and that motor 41 will drive register 49 forward approximately three-fourths of the time and motor 46 will drive it in the reverse direction approximately one-fourth of the time during each cycle. The average result is that register 49 is advancedby an amount proportional to the displacement of brush 44 from brush 43. When the brushes 43 and 44 are together, the average advance of register 49 per cycle will be zero. When the brushes are displaced 180 degrees, register 49 will be advanced continuously.

Since the two motors 46 and 41 have the same speed, have similar starting and stopping characteristics, and are energized by a common constant-frequency source, accurate integration over appreciable time periods results.

It will be evident that,-if relay 45 were connected in series with relay l2 and brushes '30 and 3|, meter 25 would produce an indication and register 49 an integration of the same measurement. In this case, the brushes 43 and 44 could be used for transmitting some other measurement to an additional relay. I have shown another receiving relay 5| connected in series with relay l2, the relays I2 and 5| being assumed to be located at. different receiving points; The relay 5| controls a somewhat different type of differential-measuring apparatus. When the relay is energized, a charging circuit from a source 52 is closed to a condenser 53. When the relay is deenergized, a discharge circuit for the condenser is closed through a resistance 54. A suppressed-zero heavily-damped millivoltmeter 55 is connected across the condenser and measures the average charge thereof. The average charge on the condenser will be proportional to the difference between the charging and discharging times and, by suitably proportioning the capacity of the condenser and the discharge resistance, accurate measurements proportional to the quantity transmitted will result.

At 56 is another series-connected relay controlling a heater circuit like that controlled by relay l2. However, the thermocouples 2| and 22 are connected in series-opposition to a single-coil millivoltmeter 51, which is less expensive than the double-coil differential instrument 25. The differential function occurs in the series thermocouple circuit which sends a current through the instrument 51 proportional to the difference of the voltages of the two thermocouples.

The relay 45, which controls the integrating register 49, is provided with an extra contactor 58 for controlling an indicator receiver like that controlled by relay 56. Thus the measurement transmitted from contacts 43 and 44 is integrated and indicated at the receiving station or stations.

It will be noted that the impulses sent out from the transmitter occur periodically, for example, once per second, although the duration of each impulse may vary in accordance with some variable being transmitted. I may, therefore, utilize the timing function which is inherent in the constant impulse rate to operate impulse-timing devices at any place where such impulses are received. This will be found useful for the driving of recording charts, operating of time switches,

for establishing the resetting interval of time meters, for indicating time, etc. At 60, inFig, 4,

type operated by relay 45. Impulses are received by the relay 45 once per second in the system as previously described andthe plunger of the relay may operate a simple ratchet mechanism in the clock once per second, which mechanism is then geared to the clock hands or other timing mechanism in the proper relation to indicate time. Where timing "devices are operated off of the impulse telemetering circuit, it will be advisable to limit the displacementof the brushes 43 and 44 to slightly less than 180 degrees so that there will never be a condition where the circuit is continuously energized as in the case of exact 180degrce displacement of the brushes. This is of no particular disadvantage with respect to thetelemetering system because it is only necessary to limit the displacement of the brushes by a few degrces'less than 180 in order to always transmit time impulses. When used for this purpose, the transmitter serves in addition as a master clock.

In accordance with the provisions of the patent statutes. I have described the principle ,of operation of my invention together with the apparatus which I now consider to represent the best emhodment thereof but I desire to have it understood thet the apparatus shown is only illustrative and that the invention may. be carried out by other means.

What I claim is new and desire to secure by Letters Patent of the United States;

'1. A telemetering system comprising, ,a transmitter, a telemetering circuit, receiving apparatus, and a source of supply for the telemetering circuit and rece'ving apparatus, the transmitter compris ng means for opening and closing the telemetering circuit and repeating such opening and closing cycle continuously-at a constant rate together with means for progressively varying the opening and closng period relation per cycle from a relation where these periods are equal to a relation where the open period is reduced to zero and the closing period is increased to the full time of the cycle, the receiving apparatus comprising a relay which is energized and deenergized in accordance with the circuit-closing and opening operations of the transmitter, and differential electrical measuring means having opposing energizing circuits respectively energized through said relay as the relay is energized and deenergized for producing a measurement proportional to the difference between the time the relay is'energized and the time it is deenergized.

2. In a telemetering system, a transmitter com- I have indicated a timing device of the impulse prising a rotary commutator having a conductl ing surface extending over an arc of 180 degrees, a pair of relatively adjustable brushes positioned to make contact with said conducting surface as the commutator is rotated, means for rotating said commutator at constant speed, and a telemetering circuit including a source of supply, one side of said circuit being connected to said conducting surface and the other side being connected in parallel tosaid brushes whereby the said commutator a telemetering circuit including a source of supply, said brushes being connected in parallel to one side of said circuit and the conducting segment of the commutator being connected to the other side of said circuit, means for driving said commutator at a constant speed, means for controlling the spacing of said brushesabout the commutator in response to the summation of two variables, and receiving apparatus associated with .said circuit and responsive to the impulses transmitted thereover for producing a measurement corresponding to the relative spacing of said brushes.

4. In a telemetering system, a receivercomprising a double-throw switch, a relay for operating said switch'which, when energized, moves the switch to one position and, when deenergized, moves the switch to the other position, a source of supply, a pair of heater circuits alternately energized from said source through said two-way switch as the relay is energized and deenergized, a thermocouple associated with each heater circuit so as to respond to the heat generated, and a measuring instrument connected to said thermccouples so as to beresponsive to the difference in heating in the two heater circuits.

5. In a teiemetering system, a transmitter comprising a commutator having a conducting segment extending over 180 degrees of its commutating surface and an insulating segment extending over the remaining portion of its commutating surface, a stationary contact bearing on said surface, a movable contact bearing on said surface, means responsive to a variable to be transmitted for moving the movable contact about the commutator awayfrom and towards the stationary contact as the variable increases and decreases respectively, a telemetering. circuit including a source of supply, means connecting said contacts in parallel to one side of said circuit and the conducting segment of the commutator to the other side of said circuit, and means for rotating said commutator at a constant speed.

6. In a telemetering system, a transmitter comprising a commutator device for periodically transmitting current impulses varying in duration from per cent to slightly less than per cent of the time of the periodic transmitting cycle, a receiver responsive to the duration of such impulses in terms of said variable, a timing device operated by said receiver and responsive to the frequency but not the duration of such impulses, and a communicating channel between said transmitter and receiver.

7. In a telemetering system, a transmitter com prising a commutating device having a part rotated at constant speed and a plurality of pairs of brushes bearing on said rotating part, the brushes of a pair being relatively adjustable with respect to 'each'other'about said rotating part, the rotating part having a conducting segment which extends over an arc of about dereessuch that ,it makes contact with a brush through one-half of each revolution, said device serving to transmit periodic current impulses over each pair of brushes, the duration of an impulse varying with the displacement of the pair of brushes through which it-is transmitted, the brushes of one pair'being adjustable independ ently of the adjustment of the brushes of a ditfei ent pair. I I

"8.-A telemetering system comprising a transmitter having means for periodically transmitting current impulses and varying the duration of such impulses over a range between 50 and nearly 100 per cent of the duration of the impulse cycle of such transmitter in responseto a variable to be transmitted, a communicating channel over which such impulses are transmitted including a relay device responsive thereto, means controlled by said relay in response to the difference in the time duration of such impulses and the time duration remaining in the impulse cycle for measuring such difference in terms of the variable transmitted, and a timing device operated by said relay in accordance with the rate at which such impulses are transmitted.

CLYDE E. STEWART. 

